Field of the Invention
The present invention relates to a vacuum grip system for gripping at least one object. The vacuum grip system has a base unit to which are affixed at least two suction units, each having at least one suction gripper. The suction units are disposed at right angles to one another, whereby at least one of the suction units grasps the object or objects to be gripped from above, and at least one of the suction units grasps the object or objects to be gripped from a lateral side.
The invention further relates to a handling apparatus for handling at least one object using a vacuum grip system, whereby the vacuum grip system is affixed to one arm of a handling robot or an overhead robot. Such handling apparatuses are used in various applications. xe2x80x9cHandlingxe2x80x9d is primarily understood to mean picking up or suctioning, lifting or turning, moving or fixing, or palletizing or depalletizing.
For the vacuum grip system of the aforementioned type, the suction grippers or suction units are, for example, constructed as flat suction grippers, accordion-pleated suction grippers, or specialized suction grippers. Flat suction grippers are particularly suited for accepting horizontal forces. The seal between the flat suction gripper and the object to be gripped can be constructed as a single sealing lip (for objects with a smooth surface such as sheet metal, cardboard boxes, glass sheets, or lumber), as a sealing edge (for objects with a rough, textured surface such as wood, stone, textured glass, or corrugated sheet metal), or as a double sealing lip (for flexible objects such as oxidized sheet metal). Accordion-pleated suction grippers are particularly adaptable to objects having uneven surfaces. Applying suction to the object to be gripped also produces a lifting effect. Accordion-pleated suction grippers are especially suited for gripping large-surface, flexible objects. Specialized suction grippers are adaptable in material, shape, and support surface for special applications such as high temperatures, chemical applications, and handling of CDs, film, or paper.
The suction units of the vacuum grip system of the aforementioned type are disposed at right angles to one another, whereby at least one of the suction units grasps the object or objects to be gripped from above, and at least one of the suction units grasps the held object or objects from a lateral side. Such grippers are also known as angled grippers. Angled grippers having two suction units are advantageous in that they securely grip the object to be gripped from the top and from the side, as well as grip the object from only one side, thus allowing flexible palletizing of the object to be gripped (so-called xe2x80x9cpick to palletsxe2x80x9d) to be easily performed. In order to enable flexible palletizing of the object, the object to be gripped must be capable of contacting other objects already laid on a pallet on either the left or right side of the object. This is not possible if the gripped object is grasped not only by the suction unit on the front sides, but also by additional suction units on the left and/or right side, or gripped on the top side and on at least two lateral sides. In known angled grippers of current art, the suction grippers are disposed at a fixed distance from one another.
The object of the present invention is to develop and further elaborate upon a vacuum grip system of the aforementioned type, such that objects of differing dimensions can be easily gripped using the vacuum grip system, and that the vacuum grip system can at the same time hold a gripped object securely and reliably.
This object is achieved by the present invention, proceeding from the vacuum grip system of the aforementioned type, by affixing suction units to a base unit such that, in order to grip at least one object, the distance between the suction unit or units on the top side of the object or objects, and the suction unit or units on the lateral side of the object or objects, may be varied.
For the vacuum grip system according to the present invention, the distance between the suction units may be adjusted in such a manner, for example, that the suction unit or units on the top side of the object is displaceably constructed parallel to the top side, and/or the suction unit or units on the lateral side of the object is displaceably constructed parallel to the lateral side. Moving the suction units away from one another increases the distance, and moving the suction units toward one another decreases the distance.
For the vacuum grip system, one or several suction units may be affixed on the top side as well as on one lateral side. Each of the suction units has at least one suction gripper, generally known from the current art. The vacuum grip system can grip one or several objects. Such an object may be a single rectangular carton or an essentially rectangular carton pallet, for example, upon which goods are arranged and bonded to the carton pallet by means of a plastic film. However, such an object may also be an essentially rectangular sack or an essentially rectangular bag.
The vacuum grip system according to the present invention has the advantage that the distance between the suction unit or units on the top side of the object or objects, and the suction unit or units on the lateral side of the object or objects can be increased, provided that the dimensions of the object or objects to be gripped permit this. The object is thereby gripped with a large lifting arm between the suction units on the top side of the object and the suction units on the lateral side of the object, thus enabling significantly more secure lifting and holding. Depending on the height of an object to be gripped, an optimal distance between the suction units on the top side of the object and the suction units on the lateral side of the object may be set.
Depending on the orientation of the object to be gripped, the suction units of the inventive vacuum grip system grip the object on a longitudinal side or on a transverse side. xe2x80x9cTransverse sidexe2x80x9d is understood to mean the shorter side of the object. In order to allow the suction unit to grip the object independent of the side at which the vacuum grip system grasps the object, it is assumed that the gripped side is the transverse side of the object. If the gripped side is in fact a transverse side of the object, the suction units grip the object at the center of that side. However, if the gripped side is a longitudinal side of the object, the suction units grip the object slightly off-center on that side.
According to an advantageous development of the present invention, it is proposed that the vacuum grip system have two suction units, each having at least one suction gripper, for gripping an object, whereby one of the suction units grasps the object from above, and one of the suction units grasps the object from the side. According to this development, the inventive vacuum grip system is thus limited to the gripping of an object. The surfaces of the suction units should be dimensioned so that, on the one hand, they are large enough to hold even large objects securely and reliably, and on the other, they are small enough not to project over the sides of small objects.
Gripping of individual objects having greatly varying dimensions is particularly important, especially in goods distribution centers for supermarkets. There, all the assortments of supermarket goods are sorted by type of good and arranged on pallets. For individual supermarkets, pallets must be prepared with various goods from the goods distribution centers. For this purpose a handling apparatus, for example, may be used having a handling robot or overhead robot, on whose arm is attached a vacuum grip system according to the present invention. Large goods themselves constitute an object that can be gripped by the vacuum grip system. For smaller goods, several goods are packed into one unit of goods, which then constitutes an object.
The vacuum grip system grasps the objects on the pallet from the goods distribution center. The robot maneuvers the vacuum grip system along with the gripped object to a pallet from the supermarket, and the vacuum grip system releases the object there (so-called xe2x80x9cpick to palletxe2x80x9d). It is also conceivable for the robot to maneuver the vacuum grip system along with the gripped object to a conveyor belt, where the vacuum grip system releases the object (so-called xe2x80x9cpick to beltxe2x80x9d). Another robot at the end of the conveyor belt takes the object from the conveyor belt and sets the object down on a pallet from the supermarket.
According to a further advantageous development of the present invention, it is proposed to vary the distance between the suction unit on the top side of the object and the suction unit on the lateral side of the object, such that the suction unit on the lateral side of the object always grasps on the lower area of the object. In this development, an object with any given dimensions is always gripped with the most optimal lifting arm, thus making lifting and holding significantly more secure. This development further ensures that for an object designed as a rectangular carton pallet upon which goods are arranged and bonded to the carton pallet using a plastic film, the suction unit always grasps on the side of the object, and not on the plastic film. The goods arranged on the carton pallet frequently have a shape that deviates from a rectangle, so that the plastic film does not form a flat surface on the side of the object. It is understood that such an object can be gripped much better and more securely on the relatively flat carton pallet than on the plastic film.
According to a preferred embodiment of the present invention, it is proposed that the vacuum grip system for gripping an object have at least two upper suction units and at least two side suction units, each having at least one suction gripper, whereby the distance between the individual suction units parallel to the top side of the object, and/or the distance between the individual suction units parallel to the lateral side, may be varied. In this manner, the effective suction area of the suction units on the top side or lateral side of the object may be increased.
According to a further advantageous embodiment of the present invention, it is proposed that the suction unit on the top side of the object be guided in a vertically-movable fashion at the base unit of the vacuum grip system and be fixable at a certain height, and that the suction unit on the lateral side of the object be attached to the base unit at a fixed height. The suction unit on the top side of the object (upper suction unit) is preferably located at its lowest position before gripping the object. In this position, the suction unit is held either by its own weight or additionally by spring tension. The vacuum grip system according to this embodiment is maneuvered down from above to the object to be gripped. In this manner, the upper suction unit comes to rest against the upper side of the object at a specified time. The vertical position (z position) of the vacuum grip system is determined at that time, and the vacuum grip system is maneuvered further down, depending on the height of the object to be gripped, until the suction unit on the lateral side of the object (lateral suction unit) is situated at the lower area of the object. The upper suction unit is thus displaced upward, relative to the base unit of the vacuum grip system.
As soon as the lateral suction unit has reached the lower area of the object, the upper suction unit is fixed in its position. If a robot is used to maneuver the vacuum grip system, according to this embodiment of the invention the vertical displacement of the upper suction unit is thus effected passively, that is, without a displacement means, but rather by maneuvering of the robot.
Alternatively, it is proposed that the suction unit on the top side of the object be fastened to the base unit of the vacuum grip system at a fixed height, and that the suction unit on the lateral side of the object be guided in a vertically-movable fashion at the base unit and be fixable at a certain height. The lateral suction unit is preferably situated in its highest position before grasping the object. The vacuum grip system according to this alternative embodiment is maneuvered down from above to the object to be gripped. In this manner, the upper suction unit comes to rest against the upper side of the object at a specified time. The vertical position (z position) of the vacuum grip system is determined at that time, and the lateral suction unit is maneuvered downward, depending on the height of the object to be gripped, until the lateral suction unit is situated at the lower area of the object.
Vertical displacement of the suction unit on the top side of the object, or of the suction unit on the lateral side of the object, is achieved according to another embodiment of the invention by a displacement means. The displacement means is preferably constructed as at least one pneumatic cylinder that is disposed between the base unit of the vacuum grip system and the suction unit. Alternatively, it is proposed to construct the displacement means as an electric motor that vertically displaces the suction unit by means of a gear arrangement.
As soon as the lateral suction unit reaches the lower area of the object, the suction unit is brought to rest against the side of the object. For this purpose, according to a preferred embodiment of the present invention it is proposed to guide the suction unit on the top side of the object, displaceable parallel to the top side, at the base unit of the vacuum grip system. In order to bring the lateral suction unit to rest against the side of the object, the entire vacuum grip system is displaced in the direction to the side of the object until the lateral suction unit contacts the side of the object. The upper suction unit is thus displaced parallel to the top side of the object.
Alternatively, it is proposed to guide the suction unit on the lateral side of the object, displaceable perpendicular to the lateral side, at the base unit of the vacuum grip system. In order to bring the lateral suction unit to rest against the side of the object, the lateral suction unit is displaced in the direction to the side of the object until the lateral suction unit contacts the side of the object.
As soon as the suction units contact the top side or lateral side, respectively, of the object, the suction units can be fixed in their positions and the suction grippers can be evacuated. The object is gripped and held securely by the vacuum grip system according to the invention. The gripped object can be lifted by appropriate movements of a robot on whose arm is attached the vacuum grip system.
According to a further advantageous development of the present invention, it is proposed to affix to the base unit of the vacuum grip system a mechanical undergripper that is at least partially displaceable underneath at least one of the objects lifted by the suction unit. As soon as the undergripper is pushed thereunder, the lifted objects can be set down on the undergripper. Since the location (position and orientation) of the undergripper is known, after the object is set down on the undergripper the angle of wobble of the object about the axes that run parallel to the top side of the object can be determined. More precisely, the angle of wobble about the x-axis (angle of wobble c) and about the y-axis (angle of wobble b) can be determined. The suction units are relieved when the object is set down on the mechanical undergripper. The suction units now perform only a holding function; that is, they hold the objects on the undergripper during the handling motions of the robot. The suction units need no longer perform a support function, that is, to support the full weight of the objects. By the use of the mechanical undergripper, the objects can be held and handled significantly more securely and reliably by the vacuum grip system.
The vacuum grip system according to this development has a base unit and at least one suction unit affixed to the base unit, each suction unit having at least one suction gripper. This vacuum grip system as well has suction units, advantageously disposed at right angles to one another, at the top side of the object or at one lateral side of the object, the distance between the suction units being adjustable. Even without these features, the vacuum grip system with the mechanical undergripper has the stated advantages of the characteristics of claim 1. Protection of the patent, therefore, should relate to a vacuum grip system of the latter described art having only one suction unit, and for which the listed features are lacking in the characteristics of claim 1.
According to a preferred embodiment of the present invention, it is proposed that the depth of the telescoping motion of the undergripper be variable. Additionally or alternatively, it is proposed that the width of the undergripper be variable. To vary the width of the undergripper, it is proposed that the undergripper be constructed as a lattice grate. As a further option for varying the width of the undergripper, it is proposed that the undergripper be constructed as a plate that is divided into at least two longitudinal partial plates that can be moved under, over, or into one another.
As a final option for varying the width of the undergripper, it is proposed that the undergripper be constructed as a fork having at least two tines, whereby the distance between the tines may be adjusted to vary the width of the undergripper. The undergripper is preferably constructed as a fork having at least two tines, whereby the tines can be sequentially telescoped outwardly or inwardly. The depth of the telescoping motion of the individual tines may be varied.
For flexible objects, a combination of tines on the undergripper whose distance may be varied and which may be sequentially telescoped outwardly offers considerable advantages. For flexible objects, the side of the object lifted by the vacuum grip system might not be lifted over its entire width, but instead might still lie on its edge, for example, on the support surface.
First, the distance between the tines is set to a small value. Then, one or several of the tines are telescoped outwardly under the lifted part of the object. Then the distance between the tines under the object is increased, whereby the tines slide along the underside of the object. The areas of the object that previously had lain on the support surface are thus lifted.
To simplify pushing the undergripper under the object, according to a advantageous development of the invention it is proposed that the undergripper have on its top side a means for reducing friction between the undergripper and the object, at least while the undergripper is being pushed under the object. The friction-reducing means can be designed, for example, as a specialized coating on the surface, at least on the top side of the undergripper. The means may also be designed as rollers or balls that are affixed to the top side of the undergripper and rotatably mounted.
According to a preferred embodiment of the invention, it is proposed that the vacuum grip system have a means for moving the object onto the undergripper. According to this embodiment, the undergripper is not pushed under the object, but rather, the object moves onto the undergripper. The movement means is designed, for example, as driven rollers or balls, or as a conveyor belt on the top side of the undergripper.
So that the mechanical undergripper does not collide with other objects on the pallet during palletizing or depalletizing, according to a further preferred embodiment of the invention it is proposed that the width of the undergripper be less than or equal to the width of the object lifted by the suction units.
According to a further advantageous development of the present invention, it is proposed that the vacuum grip system have an identification means for determining the width of the lateral side of the lifted object on which the suction unit grasps. Depending on the width of the object, the width of the mechanical undergripper can be adjusted. Also, if the dimensions of the gripped object are known, based on the width of the object that is determined by the identification means, the particular orientation of the object, that is, whether the object was gripped on a transverse side or on a longitudinal side, can be checked. If the gripped side is the longitudinal side of the object, the suction units can reach around to grasp the object closer to the center of the gripped side. In this manner, it can be assured that the object grasped by the suction units is completely lifted on the gripped side, thus allowing the mechanical undergripper to be easily pushed under the object.
According to a further preferred embodiment of the present invention, it is proposed that the identification means have a plurality of tracer pins adjacently arranged and swivelable about a common rotational axis, whereby a portion of the tracer pins contacts the surface of the object lifted by the suction units, and the other portion of the tracer pins are swiveled down next to the object. The axis of rotation of the tracer pins preferably runs parallel to the gripped side of the object. Furthermore, the axis of rotation preferably runs as high as the top side of the gripped object. The width of the gripped side of the object can be determined from the swivel position of the individual tracer pins. The more tracer pins the identification means has, the more accurately the width of the gripped side can be determined.
According to yet another preferred embodiment of the present invention, it is proposed that the undergripper, as a result of its own weight or by a displacement means, is guided in a vertically-movable fashion at the base unit of the vacuum grip system. Before the undergripper is pushed under the lifted object, the undergripper is moved to the correct vertical position so that the undergripper will fit in the gap between the underside of the lifted object and the former support surface of the object. The z position of the top side of the object is known from the vertical position of the upper suction gripper. If the dimensions of the object are also known, the correct vertical position of the undergripper can be determined.
Advantageously, at the base unit of the vacuum grip system a stop, which is vertically displaceable and fixable at a specified height, is guided that limits displacement of the undergripper from below. The stop is moved to a vertical position and fixed in the position such that the undergripper comes to rest on the stop at the correct vertical position. The undergripper preferably moves automatically as a result of its own weight until it comes to rest against the support on the stop.
Alternatively, it is proposed to effect vertical displacement of the undergripper or stop by a displacement means. The displacement means is preferably constructed as at least one pneumatic cylinder that is disposed between the base unit of the vacuum grip system and the undergripper, or between the base unit and the stop. Alternatively, it is proposed to design the displacement means as an electric motor that vertically displaces the undergripper or the stop by means of a gear arrangement.
By means of the upper suction unit and the mechanical undergripper, it is already possible to determine the vertical position and two angles of wobble of the object. In order to allow further handling (for example, palletizing by xe2x80x9cpick and palletxe2x80x9d) of the gripped object, the location of the object must be known. In order to determine the location of the object, the transverse and longitudinal positions and the rotational angle of the object also must be determined. To this end, according to an advantageous development of the present invention it is proposed that the vacuum grip system have fine localization means to arrange the lifted object in a predetermined location. Preferably, the fine localization means is constructed as two flat stop elements, disposed at right angles to one another and at a right angle to the undergripper, which are affixed to the base unit of the vacuum grip system, whereby the sides of the object may be moved to rest against the surfaces of the stop elements.
As an alternative method of determining the location of the object, it is proposed that the vacuum grip system have fine localization means to determine the location of the object to be gripped. Advantageously, the fine localization means is constructed as two flat stop elements, disposed at right angles to one another and at a right angle to the undergripper, mounted on the base unit of vacuum grip system, whereby the surfaces of the stop elements may be moved to rest against the sides of the object, and means for determining the swivel position of the stop elements are provided. The means for determining the swivel position of the stop elements are preferably designed as path sensors, whereby it is preferred that one path sensor is respectively affixed on each stop element, on both sides of the vertical axis, between the stop element and the base unit of the vacuum grip system. Complete fine localization of the object may be performed with a total of three path sensors on both stop elements; that is, with two path sensors on one of the stop elements and one path sensor on the other stop element.
It is conceivable to construct the fine localization means not as a part of the vacuum grip system, but rather, independently of the vacuum grip system. For fine localization, the gripped object could be transported to the fine localization means, for example by maneuvering the robot or by a conveyor belt upon which the object is set down by the vacuum grip system, whereupon fine localization is performed.
To simplify the vacuum grip system according to the invention, it is proposed that the suction unit on the lateral side of the object be constructed as one of the flat stop elements of the fine localization means. It is further proposed that at least one of the flat stop elements be swivel-mounted on the base unit of the vacuum grip system, between an operating position and a rest position.
Preferably, the stop element forming the lateral suction unit is not swivel-mounted. The other stop element, on the other hand, is swivel-mounted, and can be swiveled to a position wherein the stop element does not interfere with gripping and lifting of the object, pushing down the undergripper, and setting the object down on the undergripper, as long as the stop element is not needed.
According to a preferred embodiment of the present invention, it is proposed that the fine localization means be constructed as tracer sensors. At least three each of the tracer sensors are arranged in two planes that are disposed at right angles to one another. The tracer sensors may brought to rest against the sides of the object to be gripped. To this end, either the tracer sensors may be moved to the sides of the object to be gripped, or the object to be gripped may be moved to the tracer sensors. The tracer sensors can be actively moved to the sides of the object, using displacement means. Alternatively, the tracer sensors can be displaced passively, using a handling robot. For this purpose, the tracer sensors, together with the vacuum grip system, are moved by the handling robot to the sides of the object to be gripped until they come to rest against the sides. The vacuum grip system according to the proposed embodiment also has a means for evaluating the output signals of the tracer sensors. As soon as the tracer sensors make contact with the sides of the object to be gripped, the output signals of the tracer sensors change. When all tracer sensors have made contact with the sides of the object, the transverse and longitudinal positions and angle of rotation, and thus the location, of the object to be gripped can be determined. With the proposed embodiment, fine localization of the object can be performed, even before the object is lifted or set down on the undergripper.
According to yet another advantageous development of the present invention, it is proposed that the vacuum grip system have a sensor for selecting one of the objects to be gripped by the suction units of the vacuum grip system, from objects arranged on a pallet, and for rough localization of the selected object. The sensor performs rough localization of the selected object before fine localization or before the actual gripping operation. The object is thereby localized with an accuracy of several centimeters. It is also conceivable to affix the sensor not directly to the vacuum grip system, but rather to the robot arm.
According to a preferred embodiment of the present invention, it is proposed that the sensor be designed as a laser sensor that scans over the objects on the pallet with a laser beam, whereby means is provided to detect the transit time of the laser beam, so that from the transit time the shape of the surfaces of the objects arranged on the pallet may be determined, and that the object to be gripped by the suction units of the vacuum grip system may be selected from the objects arranged on the pallet, according to a specified ranking order. The laser sensor scans obliquely from above, ideally at a scanning angle of approximately 45xc2x0, over the surface of the pallet. For rough localization, however, satisfactory results are still obtained with a scanning angle of approximately 20xc2x0. The arrangement of objects on the pallet can be determined from the shape of the surfaces of objects arranged on the pallet, when the dimensions of the objects are known. An object is selected from the objects arranged on the pallet according to a specified ranking order.
The object is preferably selected according to the ranking order of upper, front, right. That is, the objects arranged uppermost on the pallet are selected first. Of these upper objects, those that lie closest to the front are then selected. Of these upper, front objects, the object lying farthest to the right is then selected. The vacuum grip system thereby affords particularly good accessibility of objects on the pallet. From the upper, front objects, those that lie farthest to the left could also be selected without limiting accessibility.
For rough localization of the selected object, according to a preferred embodiment it is proposed that the objects have an essentially rectangular design, and that the sensors roughly localize the location (position and orientation) of the edges at the upper, front, right corner of the selected object. These three edges form a tripod by which the location of the corner of the selected object is unambiguously determined. However, this locational determination of the corner can only serve as a rough localization. Fine localization is performed following rough localization by gripping and setting the object down on the undergripper, as described above.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.